Revert 133468 - Fix wallpaper fade animation flashing problem.

ash/desktop_background/desktop_background_controller.cc

Index: ash/desktop_background/desktop_background_controller.cc
===================================================================
--- ash/desktop_background/desktop_background_controller.cc	(revision 133513)
+++ ash/desktop_background/desktop_background_controller.cc	(working copy)
@@ -29,11 +29,14 @@
 void DesktopBackgroundController::SetDesktopBackgroundImageMode() {
   internal::RootWindowLayoutManager* root_window_layout =
       Shell::GetInstance()->root_window_layout();
+  if (root_window_layout->background_widget())
+    root_window_layout->background_widget()->Hide();
   int index = Shell::GetInstance()->user_wallpaper_delegate()->
       GetUserWallpaperIndex();
   root_window_layout->SetBackgroundLayer(NULL);
-  internal::CreateDesktopBackground(GetWallpaper(index),
-                                    GetWallpaperInfo(index).layout);
+  root_window_layout->SetBackgroundWidget(
+      internal::CreateDesktopBackground(GetWallpaper(index),
+                                        GetWallpaperInfo(index).layout));
   desktop_background_mode_ = BACKGROUND_IMAGE;
 }